<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
  </head>
  <body>
    <p>
      "这是一个开始"
    </p>
    <script>
      document.write("<h1 id='test-head-1'>这是标题</h1>");
      document.write("<p>这是段落</p>");
    </script>
    <button type='button' onclick="alert('Welcome!')">点击这里</button>
    <button type='button' onclick="Myfun()">改变标题内容</button>
  </body>
  <script>
    function Myfun(){
      x=document.getElementById("test-head-1");
      x.innerHTML="Hello World!";
    }
  </script>
</html>
